We aim to determine the effectiveness and cost-effectiveness of multilevel botulinum-toxin type A injections in combination with a 12-week period of intensive functional
physiotherapy exercises (BtA+iPT) and compare this with the effectiveness and cost-effectiveness of only a 12-week period of intensive functional physiotherapy exercises (iPT) in young children with
spastic Cerebral Palsy (4-12 years).

A 2-group RCT will be conducted: one intervention group will receive combined multilevel BtA+iPT treatment (multiple botulinum toxin injections followed by a 12-week period of intensive physiotherapy
exercises according to a standardized protocol of on average 4 hours per week) and the other intervention group will only receive the iPT component as treatment. The children will be recruited via (waiting lists of ) the BtA-consulting hours in Amsterdam and Rotterdam, and when necessary via affiliated CP treatment centers in the Netherlands. The current BtA-iPT intervention protocol is standardized.

- Primary outcome

Primary measures are:
1. Functional health status as measured by the Child Health Questionnaire (CHQ) Child and Parent Forms;
2. A condition-specific DISABKIDS health related quality of life questionnaire for CP;
3. The level of actually performed everyday physical activities (‘actual performance’) as measured with valid and reliable several-day ambulatory monitoring techniques;
4. Gross motor functioning as measured using the Gross Motor Function Measure (GMFM66).
Cost-utility analyses will be done using costs per quality adjusted life year (QALY) as primary outcome measure. The Health Utilities Index (HUI) will be the primary outcome measure for the economic evaluation.